Hi Robert.
First of all: a good source for new add-ons is Orbit hangar:
http://www.orbithangar.com
@Graphics: Keep in mind that Orbiter is not a fancy new video game or something. Its a free simulator so don't expact too impressive graphics. You can however, improve some things by downloading new textures for the planets (Level10 and up textures) and the sun etc. Check orbit hangar for packages.
Also make sure to enable the settings in the "visual effects" tab. If you want to improve your frame rate on a vista system, you will want "VistaBoost", you can find it at orbit hangar too.
@Ships: I can understand that you are looking for new vessels and aircraft, but everyone will tell you: the best way to start with orbiter is the stock delta glider which comes with the orbiter simulator. Most other vessels are MUCH more harder to use and require some more skill.
If you still can't wait, you may want to try these vessels out:
DeltaGlider IV :
http://orbiter.dansteph.com/index.php?disp=dgIII
Improved and a little bit more realistic delta glider.
XR1/2/5:
http://www.dougsorbiterpage.com/
Well done new ships.
If you are interested in the space shuttle, you should def try to the stock Atlantis first. There are "Shuttle Fleet" and "Space Shuttle Ultra" at orbit hangar but they require much more skill and experience and are not suitable for a beginner (I guess).
Have fun
